In fact, researchers from Harvard-affiliated McLean Hospital found that members of the Native American Church performed better on some psychological tests than other Navajos who did not regularly use peyote.
A 1994 federal law allows roughly 300,000 members of the Native American Church to use peyote as a religious sacrament. The five-year study set out to find scientific proof for the Navajos' belief that the substance, which contains the hallucinogen mescaline, is not hazardous to their health even when used frequently.
The study was conducted among Navajos in the Southwest by McLean psychiatrist John Halpern. It compared test results for 60 church members who have used peyote at least 100 times against those for 79 Navajos who do not regularly use peyote and 36 tribe members with a history of alcohol abuse but minimal peyote use.
Those who had abused alcohol fared worse on the tests than the church members, according to the study.
Church members believe peyote offers them spiritual and physical healing, but the researchers could not say with any certainty that peyote's pharmacological effects were responsible for their test results.
"It's hard to know how much of it is the sense of community they get (from the religion) and how much of it is the actual experience of using the medication itself," said Harrison Pope, the study's senior author and director of the biological psychology laboratory at the hospital near Boston.
The researchers argue that their findings should offer "reassurance" to the 10,000 Native American Church members serving in the military who were barred from using peyote before new guidelines were adopted in 1997.